The use of Photomultiplier Tubes (PMTs) in the construction of gamma cameras for nuclear medicine has been largely unchanged since the 1950's. Recently there has been an intensive effort by several groups including ourselves to develop various types of solid state gamma cameras because they offer vast improvements in performance, size and weight, and cost. To date gamma cameras based on solid state detectors have not achieved all of these goals because of basic limitations of the solid-state detector technologies explored so far. The performance of solid-state photodetectors is limited by noise due to their capacitance and leakage current. We have made significant progress on the development of silicon drift photodetectors (SDPs) for direct replacement of the PMT's in Anger cameras. The main advantage of these new detectors is their extremely small capacitance (independent of detector size) and low noise. However until now these devices have needed a large amount of cooling (deltaT=50 degrees C). During the proposed Phase I effort we propose to investigate a significant innovation in drift detector design that adds internal gain to the drift detector. This mitigates leakage current noise so that the new devices do not have to be cooled. We propose to fabricate test structures showing the feasibility of the approach in Phase I and to finalize the technology during Phase II. This technology will result in vastly superior performance and low cost compared to other technologies such as APDs, PIN diodes, proposed as PMT replacements in the past. These novel devices will be assembled into a 20cm diameter prototype Anger camera during Phase II. PROPOSED COMMERCIAL APPLICATION: This technology has potential for replacement of photomultiplier tubes used in conjunction with scintillation crystals for gamma-ray spectroscopy, nuclear medical imaging, photon counting, etc. The overall market for the instrumentation in these areas is in the billions of dollars. The portion of this market addressed by this technology is in the hundreds of millions of dollars.